Most played cards in Madness:

4 Decks
Lion's Eye Diamond
16 copies - 4 average
Vengevine
16 copies - 4 average
Faithless Looting
16 copies - 4 average
Blazing Rootwalla
16 copies - 4 average
Hollow One
16 copies - 4 average
Basking Rootwalla
16 copies - 4 average
Anje's Ravager
16 copies - 4 average
Wooded Foothills
13 copies - 3.25 average
Burning Inquiry
12 copies - 3 average
Street Wraith
12 copies - 3 average
Putrid Imp
12 copies - 3 average
Ancient Grudge
11 copies - 2.75 average
Firestorm
11 copies - 2.75 average
Faerie Macabre
11 copies - 2.75 average
Bloodstained Mire
10 copies - 2.5 average
Anger
9 copies - 2.25 average
Badlands
9 copies - 2.25 average
Taiga
7 copies - 1.75 average
Bone Shards
6 copies - 1.5 average
Ox of Agonas
5 copies - 1.25 average